The proposed plan of this research program is to study the laminar development of the dorsal lateral geniculate nucleus (LGN). Our aim in this program is two-fold. First, we hope to gain insight into the laminar or functional segregation of cells. Second, we wish to address the question of which developmental mechanisms are involved in this cytoarchitectural differentiaton. Our approach will involve an anatomical study of the LGN in the tree shrew using light and electron microscopic techniques. We will concentrate our study on the first ten postnatal days, the period of normal laminar differentiation in tree shrews. We will study cellular morphology, arrival of afferent connections and synaptogenesis in both normal and bilaterally and unilaterally enucleated animals. We will also address the issue of arrival of afferent connections in the prenatal animal and will study the effect of prenatal enucleations. The latter investigations should provide relevant information on the effect on subsequent visual system organization in cases of early ophthalmic damage.